To date, robots have performed a variety of works involving an assembly of components using an end effector attached to its far end. As an example of an actuator that drives an end effector, a linear actuator in which a movable portion is linearly movable relative to a fixed portion is used in some cases.
Examples of the linear actuator include a “direct drive actuator”, which directly drives a movable portion without using a decelerator.
A direct drive actuator is capable of controlling operations at high speed and with high precision and enhancing its work range when linked with a robot. On the other hand, a direct drive actuator has problems in size reduction and high power output. Moreover, objects attachable to the far end of a robot are limited to those within a specific weight range. Thus, actuators having a small size and high power output and producing a small amount of heat have been desired.
Direct drive actuators include a voice coil motor (VCM), in which only a coil reciprocates in a strong magnetic field produced by a permanent magnet, such as a neodymium magnet. A voice coil motor can be designed to have a light-weight movable portion, but is more likely to have low power output per volume and produce heat since the voice coil motor is a direct drive motor. Moreover, an end effector, such as a hand, attached to the movable portion is more likely to be heated to high temperatures as a result of heat being directly transferred to the end effector.
On the other hand, a voice coil motor disclosed in PTL 1 includes a stator having an air injection mechanism. The properties of the voice coil motor are enhanced by cooling an armature coil with air without changing the size of the motor.
A linear motor disclosed in PTL 2 includes multiple voice coil linear motor units arranged in parallel. The linear motor having this structure is designed to have high power output while restricting the volume increase and thermally separates the movable portion and the fixed portion from each other.